Forcing invalid encounter data in PS1

[etony33]

Valid enemies in PS1 range from 01 (Swarm) to 4A (Saccubus). So, what happens for values between 4B and FF if you force the game to try to bring it up? I am working on finding out. I've done a few so far:

00: Never ending box of 0 HP expands on the right, followed by the game crashing
4B: ‘ W W, glitchy Wyvern sprite, 31 HP, attacks like Wyvern but it morphs into a THUN spell animation
4C: Crash
4D: Q (glitchy blocks) XG x3, 198 HP, small glitchy blocks on left side of screen
4E: Crash
4F: Crash, then instantly starts new game with half the screen glitched out
50: Text box that says “THIS TOWN IS CALLED UZO.”, and game freeze
51: 5G 0 0, 47 HP, glitchy Wyvern sprite, everything on the screen has outline of glitchy blocks, attacks like Wyvern but it morphs into a THUN spell animation
52: Crash
53: Resets the game
54: J G G, everything else exactly the same as 51

Does anyone (lorenzo perhaps) know why these specific things happen?

[etony33]

55: Crash, then starts a new game with a green border around most of the screen
56: Resets the game
57: (glitchy blocks), 87 HP, glitchy Wyvern sprite
58: Crash
59: Reset
5A: G O O, 63 HP, glitchy Wyvern sprite, glitch border
5B: Crash
5C: Crash, reset
5D: O x6, 79 HP, glitchy Wyvern sprite and glitch border
5E: Crash
5F: Says my inventory is full, asks if “M (glitch blocks)” is not needed, then says “M (glitch blocks)” is abandoned and the game freezes

[etony33]

Hex 69 looks like this. I'm not sure what enemy it looks like, but it looks like something rather than a glitchy mess. First non-Wyvern sprite to look that way. Anyone know what it is?

[etony33]

It has Medusa's attack animation (followed by the THUN spell), so maybe that's what it is?

[etony33]

https://youtu.be/FXYFviE_XQE

A success! Hex 73 actually doesn't crash the game.

[etony33]

^That video made me discover a minor bug:

You'd have to have Alis get to level 2 with just under 50 XP, get Myau, and kill her off. Don't let her gain any XP until the fight with the Casba Dragon. She'll gain 61+ XP, thus giving her enough to advance to level 4, but she'll only go up one level.

[etony33]

00: Never ending box of 0 HP expands on the right, followed by the game crashing
4B: ‘ W W, glitchy Wyvern sprite, 31 HP, attacks like Wyvern but it morphs into a THUN spell animation
4C: Crash
4D: Q (glitchy blocks) XG x3, 198 HP, small glitchy blocks on left side of screen
4E: Crash
4F: Crash, then instantly starts new game with half the screen glitched out
50: Text box that says “THIS TOWN IS CALLED UZO.”, and game freeze
51: 5G 0 0, 47 HP, glitchy Wyvern sprite, everything on the screen has outline of glitchy blocks, attacks like Wyvern but it morphs into a THUN spell animation
52: Crash
53: Resets the game
54: J G G, everything else exactly the same as 51
55: Crash, then starts a new game with a green border around most of the screen
56: Resets the game
57: (glitchy blocks), 87 HP, glitchy Wyvern sprite
58: Crash
59: Reset
5A: G O O, 63 HP, glitchy Wyvern sprite, glitch border
5B: Crash
5C: Crash, reset
5D: O x6, 79 HP, glitchy Wyvern sprite and glitch border
5E: Crash
5F: Says my inventory is full, asks if “M (glitch blocks)” is not needed, then says “M (glitch blocks)” is abandoned and the game freezes
60: Crash
61: Crash
62: This one’s kind of interesting. It does the “pitfall” animation a few times before throwing you into a battle with Q G x3. They all have 18 HP. It seems to be a scrambled Dr. Mad sprite on the left side of the screen. When you try to attack, it just endlessly pitfalls.
63: Crash
64: Crash
65: Freeze
66: Freeze
67: Crash
68: Crash
69: Unknown enemy sprite with Medusa’s attack animation, 34 HP, and the glitch border
6A: Crash
6B: Crash
6C: Reset
6D: Reset
6E: Instantly starts a new game, but with what looks like a glitchy enemy sprite on the left side of the screen
6F: “THIS TOWN IS CALLED UZO.” is repeated twice, followed by a battle with (glitch blocks) x8, all with 154 HP and the same glitchy enemy sprite from 6E. “This town is called Uzo” is repeated ad infinitum in lieu of an action in battle.
70: Crash, reset
71: “THANKSWILL YOUPAL MA1DO YOU KNOW” keeps appearing on the screen, and there’s an enemy called “566789” that has 194 HP and a similar glitch sprite to 6E and 6F
72: Reset
73: Doesn’t glitch out! XYYZ enemy with 0 HP, a glitchy sprite, and gives a ton of XP/MST/a glitch item
74: Crash, reset
75: Trippy! Major graphical errors, ‘3F’ enemy with 61 HP
76: Freeze
77: Crash
78: Crash
79: (Glitch blocks), glitchy Sworm sprite, 19 HP, and it gives the Laconian Sword!
7A: Crash
7B: Crash
7C: Crash
7D: (Glitch blocks), 43 HP, appears to be Skeleton’s attack animation, and you win a Magic Hat
7E: Crash
7F: Reset

I posted videos for 73, 75, and 79.

[Zucca]

Whoa. You've done some work here.

79 sure was a surprise.

[etony33]

The fact that the glitch item in 73 had a different name in battle than it did on the menu screen tells me that it's reading the name of the item from RAM. I'm guessing that's why the game freezes and crashes: it attempts to overwrite something to show the enemy sprite (or to change a value related to the number of members in your party, so that it doesn't, say, spawn 3+ enemies with just Alis), and that something is in RAM, thus causing the corruption.

But I really have no idea. That's total speculation, but it would seem to make sense.

[etony33]

80-FF is exactly like 00-7F. Even the glitch enemies. Starts with Sworm at 81. Interesting.